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Abstract Detail



Developmental and Structural Section

Losada , Juan M [1], Povilus , Rebecca [2], Friedman, William E [2].

Seed development in Nymphaea thermarum, a diminutive water lily extinct in the wild  .

Unlike the vast majority of flowering plants, Nymphaeales share a fairly unique set of embryological features that include nutrient accumulation in maternal tissues of the seed (perisperm), a reduced endosperm, and a minute embryo at seed maturity. To date, the developmental relationships between the perisperm, endosperm and the embryo have not been investigated in detail in most members of this important ancient angiosperm clade. We examined Nymphaea thermarum, a small, annual water lily discovered in the mid-1980s before its extinction from its native habitat in Rwanda (Africa).  While germplasm is being maintained in a few botanic gardens worldwide, little is known of the reproductive biology of this species.   Following double fertilization, starch quickly accumulates in the nucellar tissues adjacent to the small endosperm and its continuous deposition within the perisperm proceeds centrifugally. The endosperm is ab initio cellular and highly bipolar, initiating two essentially autonomous developmental domains: a larger micropylar domain and an ephemeral chalazal domain with a haustorial morphology. During seed development, expansion of the micropylar endosperm domain eventually obliterates the chalazal domain. Concurrently, small amounts of starch begin to form in the endosperm. By the time the seed is mature, the embryo has expanded to completely fill the micropylar endosperm domain except for the single outermost layer of endosperm cells which continue to separate the embryo from direct contact with the maternal tissues of the seed.   Seed germination begins, without dormancy, six days after fruit dehiscence in N. thermarum. Starch breakdown in the perisperm is concomitant with starch accumulation in the endosperm and the two cotyledons during germination of the seed. Elongation of the hypocotyl promotes seed coat breakage and emergence of the hypocotyl along with one of the two plumular leaves prior to root elongation. Together, these results point to a crucial role for the maternal tissues of the perisperm during development and germination of Nymphaea thermarum seeds. 


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1 - Arnold Arboretum Of Harvard University, Organismic And Evolutionary Biology, 1300 Centre Street, Boston, MA, 02131, USA
2 - Arnold Arboretum of Harvard University, Organismic and Evolutionary Biology, 1300 Centre Street, Boston, Massachusetts, 02131, United States

Keywords:
Embryo
Endosperm
Perisperm
Nymphaeales
water lily
Nymphaea thermarum.

Presentation Type: Oral Paper:Papers for Sections
Session: 25
Location: Pines North/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 11:00 AM
Number: 25004
Abstract ID:362
Candidate for Awards:None


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